Remove trailing slash from OpenAPI server URLs when pathBase is empty (#64716)

* Initial plan

* Fix: Remove trailing slash from OpenAPI server URLs when pathBase is empty

Co-authored-by: captainsafia <[email protected]>

* Update snapshot test for trailing slash fix

Co-authored-by: captainsafia <[email protected]>

* Improve code comment for trailing slash removal logic

Co-authored-by: captainsafia <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: captainsafia <[email protected]>

Author: Copilot

src/OpenApi/src/Services/OpenApiDocumentService.cs

@@ -209,6 +209,12 @@ internal List<OpenApiServer> GetOpenApiServers(HttpRequest? httpRequest = null)
         if (httpRequest is not null)
         {
             var serverUrl = UriHelper.BuildAbsolute(httpRequest.Scheme, httpRequest.Host, httpRequest.PathBase);
+            // Remove trailing slash when pathBase is empty to align with OpenAPI specification.
+            // Keep the trailing slash if pathBase explicitly contains "/" to preserve intentional path structure.
+            if (serverUrl.EndsWith('/') && !httpRequest.PathBase.HasValue)
+            {
+                serverUrl = serverUrl.TrimEnd('/');
+            }
             return [new OpenApiServer { Url = serverUrl }];
         }
         else

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Integration/snapshots/OpenApiDocumentLocalizationTests.VerifyOpenApiDocumentIsInvariant.verified.txt

@@ -7,7 +7,7 @@
   },
   "servers": [
     {
-      "url": "http://localhost/"
+      "url": "http://localhost"
     }
   ],
   "paths": {

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiDocumentService/OpenApiDocumentServiceTests.Servers.cs

@@ -11,7 +11,7 @@
 public partial class OpenApiDocumentServiceTests
 {
     [Theory]
-    [InlineData("Development", "localhost:5001", "", "http", "http://localhost:5001/")]
+    [InlineData("Development", "localhost:5001", "", "http", "http://localhost:5001")]
     [InlineData("Development", "example.com", "/api", "https", "https://example.com/api")]
     [InlineData("Staging", "localhost:5002", "/v1", "http", "http://localhost:5002/v1")]
     [InlineData("Staging", "api.example.com", "/base/path", "https", "https://api.example.com/base/path")]
@@ -145,4 +145,39 @@ public void GetOpenApiServers_HandlesServerAddressFeatureWithNoValues()
         // Assert
         Assert.Empty(servers);
     }
+
+    [Fact]
+    public void GetOpenApiServers_RemovesTrailingSlashWhenPathBaseIsEmpty()
+    {
+        // Arrange
+        var hostEnvironment = new HostingEnvironment
+        {
+            ApplicationName = "TestApplication",
+            EnvironmentName = "Development"
+        };
+        var docService = new OpenApiDocumentService(
+            "v1",
+            new Mock<IApiDescriptionGroupCollectionProvider>().Object,
+            hostEnvironment,
+            GetMockOptionsMonitor(),
+            new Mock<IKeyedServiceProvider>().Object,
+            new OpenApiTestServer(["http://localhost:5000"]));
+        var httpContext = new DefaultHttpContext()
+        {
+            Request =
+            {
+                Host = new HostString("example.com"),
+                PathBase = "",
+                Scheme = "https"
+            }
+        };
+
+        // Act
+        var servers = docService.GetOpenApiServers(httpContext.Request);
+
+        // Assert
+        Assert.Single(servers);
+        Assert.Equal("https://example.com", servers[0].Url);
+        Assert.DoesNotContain("https://example.com/", servers.Select(s => s.Url));
+    }
 }